With production halted by the First World War AJS managed to develop the Model D into a popular sidecar machine and it was eventually replaced by the larger capacity AJS Model E.[1] In 1905 the Stevens Motor Manufacturing Company built a V-twin motorcycle powered by a JA Prestwich Industries Ltd motor, with leading-link front forks and a swinging fork at the rear.

[2] A new company, A J Stevens & Co (AJS), was founded in 1909 to manufacture motorcycles and at the 1912 London Motorcycle show they launched the 698cc side valve AJS Model D. Featuring cylinders at 50 degrees and chain drive to a three speed countershaft gearbox with a hand gear change, the original engines had quickly removable cylinder heads but after problems with oil leaks a more permanent head was specified for 1913.

The silencer was made from cast aluminium and the frame was a tubular 'diamond' construction, with Brampton bi-flex front forks, which had an unusual two way movement, and quickly detachable wheels.

[3] After the war ended in November 1918 and the Ministry restrictions were lifted, AJS restarted motorcycle production at a new factory at Graisley Hill in Wolverhampton and the Model D was resurrected with the capacity increased to 748cc and a new design of saddle and fuel tank.

In 1923 a cheaper version called the Model D1 was introduced and 1924 was the best year for sales, which continued to outstrip the capacity of the factory despite increasing the Graiseley Hill works to 230,000 square feet.